The present invention relates to an organic electroluminescent (EL) light emitting device and lighting equipment for performing current control of light emitting elements, and, in particular, relates to an organic electroluminescent light emitting device and lighting equipment having functionality for restoring to normal even if a low-voltage error occurs, by temporarily applying a reverse current to a low-voltage error light emitting element using a direction inverting circuit, and repairing portions in which impedance has fallen by applying the current.
In recent years, lighting equipment using organic electroluminescent devices that control a current flowing to light emitting elements at a fixed level have become known. Organic electroluminescent devices are devices which take advantage of a phenomenon in which light emission occurs due to excitons, which are created when electrons inserted into an organic material recombine with positive holes. In recent years, there has been a great deal of development of displays using organic electroluminescent devices. This is because organic electroluminescent devices have a wider viewing angle, faster response speed, and greater contrast than liquid crystal display devices.
Organic LED devices generally have a structure in which an organic layer is sandwiched between a negative pole and the positive pole. When a voltage is applied, electrons are injected as carriers from the negative pole, and positive holes are injected as carriers from the positive pole. When these recombine inside the organic layer, excitons are created and light emission occurs.
These kinds of organic electroluminescent devices are generally provided with an organic layer containing a light emitting layer, a positive hole transport layer or an electron transport layer, etc., and a pair of electrodes (negative pole and positive pole) disposed opposite one another with the organic layer in between. The organic layer normally has an extremely thin layer thickness of around 100 nm, for example. Accordingly, there is the risk of leaks between the electrodes or a lack of sufficient voltage insulation between the electrodes due to the presence of particulate matter or inconsistencies in the formation of the organic layer, to name a few examples.
When such problems occur, black spots, and dark or black lines are visible when the organic electroluminescent device is driven, thus reducing the display quality of the organic electroluminescent device. Even if black spots or the like are not visible, if there is insufficient voltage insulation anywhere there is the risk of current leakage when the organic electroluminescent device is driven. In particular, there has been a tendency for the occurrence of such problems to become more probable as organic electroluminescent devices have grown in size in recent years. This is a major problem.
In light of this situation, a method is known for fixing insulation problems between the pairs of electrodes in organic electroluminescent devices provided with a plurality of types of organic layer containing at least light emitting layers with mutually differing colors of emitted light, and pairs of electrodes disposed opposite one another with the plurality of types of organic layer in between, by insulating the badly insulated portions through application of a reverse bias voltage to the plurality of types of organic layer under differing application conditions for each color of emitted light, for example.
A manufacturing method for an organic electroluminescent element is known in which a laminated body comprising an organic layer containing a positive pole, a light emitting layer, and a negative pole, laminated in sequence, is formed on a substrate, the negative pole being formed by disposing in sequence a first conductive layer, a buffer layer, and a second conductive layer, and aging the laminated body after formation.
With this, it is possible to manufacture an organic electroluminescent element with a lower drive voltage than is conventional, by laminating in sequence the first conductive layer, the buffer layer, and the second conductive layer to form the negative pole, and then aging the laminated body after formation.
Furthermore, a lighting device has been proposed which is provided with a direct current power source means for supplying desired direct current voltage to an organic electroluminescent element, a detecting means for detecting stoppage of the voltage supply by the direct current power source means, and the reverse voltage supplying means for supplying reverse-characteristic voltage to the organic electroluminescent element when voltage supply by the direct current power source means has stopped.